In the same way you price anything today in fiat.

For example, you look around for similar things and see how much those are. If your service/product is better, you should charge more, etc.

It's all relative in the end and price is just an invented number that changes over time. Also how valuable things and services are change over time as well.

Price is simply a number used to try to convince another person to exchange their "meta-value" (money) for your goods and services so that you can trade it for other goods and services.

Money is a middleman basically, you price things accordingly.